1. Field of the Invention
This invention relates to a system for the supervising of receiving antennas said system being intended preferably for a base station in a cellular telephone system.
2. Description of the Related Art
Problems that arise generally today in antenna systems, i.e., one or more antennas including cable arrangements, for base stations in cellular telephone systems include, for instance, the supervising of parameters that describe the performance of the antennas as well as their operability together with other components in the base station. For both transmitting and receiving antennas it is desirable to be able to detect and/or to localize errors originating from, for example,
connector or cable errors, environmental influence, normal aging or physical damage; PA1 connection errors or damages in connection with antenna testing; PA1 changes in the antenna function, caused by physical obstacles to the incoming or outgoing radio wave radiation, e.g., buildings, other structures or vegetation, being added or, possibly, removed in the surroundings of the antenna; PA1 changes in the antenna function, caused by incoming radiation or other influence from other antennas or antenna systems placed in the surroundings of the antenna.
The characteristics of the antennas or antenna systems that may be influenced according to the above include, e.g., the shape of the coverage area and the transmission quality of the connected calls or the data flows.
Known means for the supervising of receiving antennas in base stations include the connection of measuring instruments for the measuring of, e.g., standing wave ratio or incoming power from the antenna. Through this manual procedure, no effective or systematic supervising of receiving antennas may be achieved whatsoever at reasonable costs.
It is further known to supervise a receiving antenna by connecting a DC voltage to the antenna from the receiving circuits, said antenna usually constituting a short circuit for direct current. The resulting direct current is sensed, giving an indication of whether the galvanic connection between the antenna and the receiving circuits is intact.
Further, in diversity antennas for receiving, as is customary in the receiving circuits, signal levels originating from the different antennas have been sensed and compared. In doing so, it has been possible to establish also antenna errors that give abnormal relations between the signal levels.
Moreover, in a transmitting antenna, which is connected or connectable to transmitting circuits for its transmitting function, sensors for the sensing of outgoing and incoming electrical signals to and from, respectively, the transmitting antenna sensors have been permanently arranged. In doing this, through the measuring of, e.g., transmitted and reflected power, it has been possible to detect errors originating at the transmitter antenna, particularly due to connector or cable errors, environmental influence, normal aging or physical damage.